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CORE-2010-0514: XnView MBM Processing Heap Overflow
From: CORE Security Technologies Advisories <advisories () coresecurity com>
Date: Mon, 14 Jun 2010 17:23:14 -0300

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

      Core Security Technologies - CoreLabs Advisory
           http://corelabs.coresecurity.com/

          XnView MBM Processing Heap Overflow



1. *Advisory Information*

Title: XnView MBM Processing Heap Overflow
Advisory Id: CORE-2010-0514
Advisory URL:
[http://www.coresecurity.com/content/xnview-mbm-heap-overflow]
Date published: 2010-06-14
Date of last update: 2010-06-14
Vendors contacted: XnView
Release mode: Coordinated release



2. *Vulnerability Information*

Class: Buffer overflow [CWE-119]
Impact: Code execution
Remotely Exploitable: Yes (client-side)
Locally Exploitable: No
CVE Name: CVE-2010-1932
Bugtraq ID: N/A



3. *Vulnerability Description*

XnView [1] is prone to a security vulnerability when processing MBM
files. This vulnerability could be exploited by a remote attacker to
execute arbitrary code on the target machine, by enticing the user of
XnView to open a specially crafted file.


4. *Vulnerable packages*

   . XnView 1.97.4
   . Older versions are probably affected too, but they were not checked.


5. *Non-vulnerable packages*

   . XnView 1.97.5


6. *Vendor Information, Solutions and Workarounds*

Update to the latest version of XnView, available on the website
[http://www.xnview.com/]


7. *Credits*

This vulnerability was discovered by Mauro Olea and researched by Mauro
Olea and Nahuel Riva from Core Security Technologies. Publication of
this advisory was coordinated by Carlos Sarraute from Core Security
Advisories team.


8. *Technical Description / Proof of Concept Code*

XnView is prone to a security vulnerability when processing MBM files.
The version used in our tests in XnView 1.97.4 running on Windows 2000
SP4. By enticing the user of XnView to open a specially crafted file, a
remote attacker may exploit this vulnerability to gain arbitrary code
execution.

The MBM file format (shortened from MultiBitMap) is a container for a
set of bitmap images. MBM files are used by most Symbian applications to
store their graphical content. MBM files can be created with the BMCONV
tool which is supplied with any Symbian (and EPOC) SDK.


8.1. *First Proof-of-Concept*

An MBM file that triggers this vulnerability is available at [2]. The
following is an excerpt of the vulnerable code, and the value of the
registers when the vulnerability is triggered (the values of EAX and ECX
are controlled by the attacker).

/-----
77FCC453   . 8901           MOV DWORD PTR DS:[ECX],EAX
77FCC455   . 8948 04        MOV DWORD PTR DS:[EAX+4],ECX
77FCC458   . 3BC1           CMP EAX,ECX
77FCC45A   . 75 25          JNZ SHORT ntdll.77FCC481



EAX 7A7A7A7A
ECX 7A7A7A7A
EDX 00000000
EBX 00000003
ESP 0171ED64
EBP 0171EEFC
ESI 013579F0 ASCII
"zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
EDI 00C60000
EIP 77FCC453 ntdll.77FCC453
C 0  ES 0023 32bit 0(FFFFFFFF)
P 1  CS 001B 32bit 0(FFFFFFFF)
A 0  SS 0023 32bit 0(FFFFFFFF)
Z 0  DS 0023 32bit 0(FFFFFFFF)
S 0  FS 0038 32bit 7FFDA000(FFF)
T 0  GS 0000 NULL
D 0
O 0  LastErr ERROR_SUCCESS (00000000)
EFL 00000206 (NO,NB,NE,A,NS,PE,GE,G)
ST0 empty -UNORM BC50 00000200 0014BC50
ST1 empty +UNORM 0014 000800EC 0049ECC0
ST2 empty +UNORM 4720 0012EF38 00000000
ST3 empty +UNORM 4730 01010052 00000014
ST4 empty 0.0000000000000000040e-4933
ST5 empty +UNORM 0018 0012EF48 77FA15EF
ST6 empty -UNORM EFB0 01010052 00000014
ST7 empty 1.0000000000000000000
               3 2 1 0      E S P U O Z D I
FST 0100  Cond 0 0 0 1  Err 0 0 0 0 0 0 0 0  (LT)
FCW 027F  Prec NEAR,53  Mask    1 1 1 1 1 1

- -----/



8.2. *Second Proof-of-Concept*

By generating a second malformed .MBM file (available at [2]), we can
trigger a heap overflow that may lead to arbitrary code execution. In
this case, the crash occurs in the following code:

/-----
77F937A5    8901            MOV DWORD PTR DS:[ECX],EAX
77F937A7    8948 04         MOV DWORD PTR DS:[EAX+4],ECX
77F937AA    3BC1            CMP EAX,ECX
77F937AC    75 2E           JNZ SHORT ntdll.77F937DC

EAX 41414141
ECX 41414141
EDX 0131DA98 ASCII
41,"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
EBX 00000005
ESP 0012DE68
EBP 0012E024
ESI 00C60000
EDI 0131DA98 ASCII
41,"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
EIP 77F937A5 ntdll.77F937A5

- -----/


The vulnerability is triggered in ntdll.dll. The code corresponds to the
function RtlAllocateHeap when a new node is added to the double-linked
list of heap chunks. As can be seen, both EAX and ECX contain arbitrary
values controlled by the attacker (0x41414141). This is the Call Stack
when the crash occurs:

/-----
Call stack of main thread
Address    Stack      Procedure / arguments          Called from
           Frame
0012E028   77FB55EB   ntdll.77F93633                 ntdll.77FB55E6
           0012E024
0012E0AC   77FA7C5E   ntdll.77FB5507                 ntdll.77FA7C59
           0012E0A8
0012E27C   77FCB167   ntdll.77F93633                 ntdll.77FCB162
           0012E278
0012E428   005AD1C6   ntdll.RtlAllocateHeap          xnview.005AD1C0
           0012E424
0012E42C   00C60000     hHeap = 00C60000
0012E430   40000060     Flags =
HEAP_TAIL_CHECKING_ENABLED|HEAP_FREE_CHECKING_ENABLED|40000000
0012E434   00000010     HeapSize = 10 (16.)
0012E464   005AD0BD   xnview.005AD0D9                xnview.005AD0B8
           0012E460
0012E46C   005AD0AA   xnview.005AD0AD                xnview.005AD0A5
0012E478   0049E8D4   xnview.005AD09B                xnview.0049E8CF
0012E748   004A00F5   ? xnview.0049E6C0              xnview.004A00F0
0012EAD4   00495075   xnview.0049FD40                xnview.00495070
0012EAE8   004C8525   Includes xnview.00495075       xnview.004C8523
0012EB24   77E12CA8   Includes xnview.004C8525       USER32.77E12CA5
0012EB44   77E14398   ? USER32.77E12C90              USER32.77E14393
0012EB48   004C8230     Arg1 = 004C8230
0012EB4C   00040124     Arg2 = 00040124
0012EB50   0000004E     Arg3 = 0000004E
0012EB54   000007D0     Arg4 = 000007D0
0012EB58   0012EC40     Arg5 = 0012EC40
0012EB74   77E14925   USER32.77E142DB                USER32.77E14920
           0012EB70
0012EB94   71715C13   USER32.SendMessageW            COMCTL32.71715C0D
           0012EB90
0012EB98   00040124     hWnd = 40124
0012EB9C   0000004E     Message = WM_NOTIFY
0012EBA0   000007D0     wParam = 7D0
0012EBA4   0012EC40     lParam = 12EC40
0012EC24   71752933   COMCTL32.717154AD              COMCTL32.7175292E
           0012EC20
0012ECB4   7175342C   COMCTL32.717528AB              COMCTL32.71753427
           0012ECB0
0012ED08   71755756   COMCTL32.7175339F              COMCTL32.71755751
           0012ED04
0012ED5C   77E12CA8   Includes COMCTL32.71755756     USER32.77E12CA5
           0012ED58
0012ED7C   77E152E6   ? USER32.77E12C90              USER32.77E152E1
           0012ED78
0012ED80   71755025     Arg1 = 71755025
0012ED84   0006012E     Arg2 = 0006012E
0012ED88   00001102     Arg3 = 00001102
0012ED8C   00000002     Arg4 = 00000002
0012ED90   00155FA8     Arg5 = 00155FA8
0012EDA0   77E15362   ? USER32.77E152A9              USER32.77E1535D
           0012ED9C
0012EDC0   0049EDED   ? USER32.CallWindowProcA       xnview.0049EDE7
           0012EDBC
0012EDC4   FFFF0201     PrevProc = FFFF0201
0012EDC8   0006012E     hWnd = 0006012E ('Tree
View',class='SysTreeView32',parent=00040124)
0012EDCC   00001102     Message = MSG(1102)
0012EDD0   00000002     wParam = 2
0012EDD4   00155FA8     lParam = 155FA8
0012EED8   77A530AA   ntdll.RtlFreeHeap              ole32.77A530A4
0012EEDC   00130000     hHeap = 00130000
0012EEE0   00000000     Flags = 0
0012EEE4   0016D990     pMemory = 0016D990
0012EEEC   77E12CA8   Includes ole32.77A530AA        USER32.77E12CA5
           0012EEF8
0012EF0C   77E14398   ? USER32.77E12C90              USER32.77E14393
           0012EEF8
0012EF10   0049ECC0     Arg1 = 0049ECC0
0012EF14   0006012E     Arg2 = 0006012E
0012EF18   00001102     Arg3 = 00001102
0012EF1C   00000002     Arg4 = 00000002
0012EF20   00155FA8     Arg5 = 00155FA8
0012EF3C   77E153A1   USER32.77E142DB                USER32.77E1539C
           0012EF38
0012EF5C   0049F0F9   Includes USER32.77E153A1       xnview.0049F0F7
           0012EF58
0012F284   004A7B45   ? xnview.0049EEC0              xnview.004A7B40
0012F294   005317E9   xnview.004A7B10                xnview.005317E4
0012FA44   00531276   xnview.005312C0                xnview.00531271
0012FA80   004C95B8   Includes xnview.00531276       xnview.004C95B4
0012FAA0   005382FE   xnview.004C9560                xnview.005382F9
0012FAB8   77E12CA8   Includes xnview.005382FE       USER32.77E12CA5
0012FAD8   77E14398   ? USER32.77E12C90              USER32.77E14393
0012FADC   005382E0     Arg1 = 005382E0
0012FAE0   00090130     Arg2 = 00090130
0012FAE4   00000401     Arg3 = 00000401
0012FAE8   00000000     Arg4 = 00000000
0012FAEC   0012FB58     Arg5 = 0012FB58
0012FB08   77E153A1   USER32.77E142DB                USER32.77E1539C
           0012FB04
0012FB28   005336BA   USER32.SendMessageA            xnview.005336B4
           0012FB24
0012FB2C   00090130     hWnd = 90130
0012FB30   00000401     Message = WM_USER+1
0012FB34   00000000     wParam = 0
0012FB38   0012FB58     lParam = 12FB58
0012FC68   005338A2   xnview.00533590                xnview.0053389D
0012FC80   004C96C7   Includes xnview.005338A2       xnview.004C96C3
0012FCA4   005369E3   xnview.004C9660                xnview.005369DE
0012FCC4   004C95B8   Includes xnview.005369E3       xnview.004C95B4
0012FCE4   005382FE   xnview.004C9560                xnview.005382F9
           0012FD18
0012FCFC   77E12CA8   Includes xnview.005382FE       USER32.77E12CA5
           0012FD18
0012FD1C   77E12DC5   ? USER32.77E12C90              USER32.77E12DC0
           0012FD18
0012FD20   005382E0     Arg1 = 005382E0
0012FD24   00090130     Arg2 = 00090130
0012FD28   00000111     Arg3 = 00000111
0012FD2C   0000000B     Arg4 = 0000000B
0012FD30   00000000     Arg5 = 00000000
0012FDA8   77E1577D   USER32.77E12CBD                USER32.77E15778
           0012FDA4
0012FDB4   0053802B   USER32.DispatchMessageA        xnview.00538025
0012FDB8   0012FDD8     pMsg = WM_COMMAND hw = 90130 ("XnView - [Browser
- - C:\Docu...") Notify =
0012FF38   005B21E2   ? xnview.005377E0
xnview.<ModuleEntryPoint>
  +0D
  0012FF3C   00400000     Arg1 = 00400000
  0012FF40   00000000     Arg2 = 00000000
  0012FF44   0013326B     Arg3 = 0013326B
  0012FF48   0000000A     Arg4 = 0000000A

- -----/


The problem is found in the function 0x65a310:

/-----
0065A310  /$  53            PUSH EBX
0065A311  |.  55            PUSH EBP
0065A312  |.  8B6C24 14     MOV EBP,DWORD PTR SS:[ESP+14]
0065A316  |.  33C0          XOR EAX,EAX
0065A318  |.  56            PUSH ESI
0065A319  |.  57            PUSH EDI
0065A31A  |.  85ED          TEST EBP,EBP
0065A31C  |.  0F8E AB000000 JLE xnview.0065A3CD
0065A322  |.  8B5C24 14     MOV EBX,DWORD PTR SS:[ESP+14]
0065A326  |.  8B7C24 18     MOV EDI,DWORD PTR SS:[ESP+18]
0065A32A  |>  8B03          /MOV EAX,DWORD PTR DS:[EBX]
0065A32C  |.  8D4C24 1C     |LEA ECX,DWORD PTR SS:[ESP+1C]
0065A330  |.  50            |PUSH EAX                      ; /Arg4
0065A331  |.  6A 01         |PUSH 1                        ; |Arg3 =
00000001
0065A333  |.  6A 01         |PUSH 1                        ; |Arg2 =
00000001
0065A335  |.  51            |PUSH ECX                      ; |Arg1
0065A336  |.  E8 284BF5FF   |CALL xnview.005AEE63          ;
\xnview.005AEE63
0065A33B  |.  83C4 10       |ADD ESP,10
0065A33E  |.  83F8 01       |CMP EAX,1
0065A341  |.  0F85 81000000 |JNZ xnview.0065A3C8
0065A347  |.  8A4424 1C     |MOV AL,BYTE PTR SS:[ESP+1C]
0065A34B  |.  84C0          |TEST AL,AL
0065A34D  |.  66:0FBEC0     |MOVSX AX,AL
0065A351  |.  7D 22         |JGE SHORT xnview.0065A375
0065A353  |.  8B13          |MOV EDX,DWORD PTR DS:[EBX]
0065A355  |.  F7D8          |NEG EAX
0065A357  |.  0FBFF0        |MOVSX ESI,AX
0065A35A  |.  52            |PUSH EDX                      ; /Arg4
0065A35B  |.  6A 01         |PUSH 1                        ; |Arg3 =
00000001
0065A35D  |.  56            |PUSH ESI                      ; |Arg2
0065A35E  |.  57            |PUSH EDI                      ; |Arg1
0065A35F  |.  2BEE          |SUB EBP,ESI                   ; |
0065A361  |.  E8 FD4AF5FF   |CALL xnview.005AEE63          ;
\xnview.005AEE63
0065A366  |.  83C4 10       |ADD ESP,10
0065A369  |.  85C0          |TEST EAX,EAX
0065A36B  |.  74 5B         |JE SHORT xnview.0065A3C8
0065A36D  |.  03FE          |ADD EDI,ESI
0065A36F  |.  897C24 18     |MOV DWORD PTR SS:[ESP+18],EDI
0065A373  |.  EB 44         |JMP SHORT xnview.0065A3B9
0065A375  |>  40            |INC EAX
0065A376  |.  0FBFF0        |MOVSX ESI,AX
0065A379  |.  8B03          |MOV EAX,DWORD PTR DS:[EBX]
0065A37B  |.  2BEE          |SUB EBP,ESI
0065A37D  |.  50            |PUSH EAX
0065A37E  |.  E8 AB4DF5FF   |CALL xnview.005AF12E
0065A383  |.  83C4 04       |ADD ESP,4
0065A386  |.  66:3D FFFF    |CMP AX,0FFFF
0065A38A  |.  74 3C         |JE SHORT xnview.0065A3C8
0065A38C  |.  0FBFC0        |MOVSX EAX,AX
0065A38F  |.  8AD8          |MOV BL,AL
0065A391  |.  8BCE          |MOV ECX,ESI
0065A393  |.  8AFB          |MOV BH,BL
0065A395  |.  8BD1          |MOV EDX,ECX
0065A397  |.  8BC3          |MOV EAX,EBX
0065A399  |.  C1E0 10       |SHL EAX,10
0065A39C  |.  66:8BC3       |MOV AX,BX
0065A39F  |.  8B5C24 14     |MOV EBX,DWORD PTR SS:[ESP+14]
0065A3A3  |.  C1E9 02       |SHR ECX,2
0065A3A6  |.  F3:AB         |REP STOS DWORD PTR ES:[EDI]
0065A3A8  |.  8BCA          |MOV ECX,EDX
0065A3AA  |.  83E1 03       |AND ECX,3
0065A3AD  |.  F3:AA         |REP STOS BYTE PTR ES:[EDI]
0065A3AF  |.  8B7C24 18     |MOV EDI,DWORD PTR SS:[ESP+18]
0065A3B3  |.  03FE          |ADD EDI,ESI
0065A3B5  |.  897C24 18     |MOV DWORD PTR SS:[ESP+18],EDI
0065A3B9  |>  85ED          |TEST EBP,EBP
0065A3BB  |.^ 0F8F 69FFFFFF \JG xnview.0065A32A
0065A3C1  |.  5F            POP EDI
0065A3C2  |.  5E            POP ESI
0065A3C3  |.  5D            POP EBP
0065A3C4  |.  33C0          XOR EAX,EAX
0065A3C6  |.  5B            POP EBX
0065A3C7  |.  C3            RETN
0065A3C8  |>  B8 04000000   MOV EAX,4
0065A3CD  |>  5F            POP EDI
0065A3CE  |.  5E            POP ESI
0065A3CF  |.  5D            POP EBP
0065A3D0  |.  5B            POP EBX
0065A3D1  \.  C3            RETN

- -----/


According to the .MBM format [3], the structure of an MBM is the
following (beginning with a Header Section):

/-----
Offset Size Data Description

0000 ID 37 00 00 10 UID1: Header Section layout

0004 ID 42 00 00 10 UID2: File kind

0008 ID 00 00 00 00 UID3: Application ID

000C L 39 64 39 47 UID4: Checksum of UID1, UID2 and UID3

0010 Offset MBM Jumptable

- -----/


The MBM Jumptable is an LListL of offsets in which each offset points to
a Paint Data Section. An LListL is basically a list where, as can be
deduced from [4], the first letter ("L") represents the encoding of the
list size indicator and the last letter ("L") represents the size of
each element of the list. In this case, we have a list of LONGs and the
size of this list is encoded as a LONG. So in our case, we have the
following:

/-----
37000010 // Header Section Layout
42000010 // File  Kind
00000000 // Application ID
39643947 // Checksum Header Section, File Kind and Application ID
14000000 // Offset to MBM Jumptable

- -----/


Our MBM Jumptable contains the following:

/-----
01000000 // List lenght
1C000000 // Offset to the list

- -----/


This is a list with one element (there is only one drawing in the file).
The structure of each Paint Data Section is described in [5]. Inside
this structure, there is a field called "Encoding", represented as Long
and which contains the following values:

/-----
00 00 00 00 Plain data
01 00 00 00 8-bit RLE encoding
02 00 00 00 12-bit RLE encoding
03 00 00 00 16-bit RLE encoding
04 00 00 00 24-bit RLE encoding

- -----/


The original value in our case was 0x00000000, that the encoding
indicates as plain data. When we change this value to 0x00007a7a, XnView
interprets the data as RLE encoding. According to the format
documentation [5]: "RLE encoding consists of sequences of marker bytes
with data bytes. A marker byte of 00 to 7F means that the next byte
should be repeated that many times and once more. A marker byte of 80 to
FF means that (100-marker) bytes of data follow."

The function 0x65A310 is responsible for handling this encoding and
copying the data indicated by the marker byte according to the encoding
indicated by the "Encoding" field. In our case, the encoding field
contains the following values:

/-----
0x00007a7a // Malformed encoding
0x7a41 // Data for this encoding

- -----/


We now look with more detail at that function, and how it handles data:

/-----
0065A347  |.  8A4424 1C     |MOV AL,BYTE PTR SS:[ESP+1C] // takes the
marker byte
0065A34B  |.  84C0          |TEST AL,AL
0065A34D  |.  66:0FBEC0     |MOVSX AX,AL                // moves it to AX
0065A351  |.  7D 22         |JGE SHORT xnview.0065A375  // checks if
it's greater than 0

- -----/


In this part, the program uses the third byte of the encoding, that is
0x7A, and since it is greater that 0, jumps to:

/-----
0065A375  |> \40            |INC EAX        // increments EAX
0065A376  |.  0FBFF0        |MOVSX ESI,AX   // copies the high part of
EAX to ESI
0065A379  |.  8B03          |MOV EAX,DWORD PTR DS:[EBX]
0065A37B  |.  2BEE          |SUB EBP,ESI
0065A37D  |.  50            |PUSH EAX
0065A37E  |.  E8 AB4DF5FF   |CALL xnview.005AF12E // obtains the byte
following 0x7A, that is the last byte of the encoding
0065A383  |.  83C4 04       |ADD ESP,4
0065A386  |.  66:3D FFFF    |CMP AX,0FFFF   // is this last byte 0xFFFF?
in fact it should be 0xFF, it's one byte
0065A38A  |.  74 3C         |JE SHORT xnview.0065A3C8 // if it is, then
good bye!
0065A38C  |.  0FBFC0        |MOVSX EAX,AX   // otherwise move AX to EAX
0065A38F  |.  8AD8          |MOV BL,AL      // AL = 0x41 goes to BL
0065A391  |.  8BCE          |MOV ECX,ESI    // ESI = 0x7B = 0x7A + 1 = ECX
0065A393  |.  8AFB          |MOV BH,BL      // BL a BH -> BH takes the
value 0x4141
0065A395  |.  8BD1          |MOV EDX,ECX    // EDX = 0x7B
0065A397  |.  8BC3          |MOV EAX,EBX    // EAX == EBX
0065A399  |.  C1E0 10       |SHL EAX,10     // here EAX == 0x41410000
0065A39C  |.  66:8BC3       |MOV AX,BX      // AX == 0x4141 -> EAX ==
0x41414141
0065A39F  |.  8B5C24 14     |MOV EBX,DWORD PTR SS:[ESP+14]
0065A3A3  |.  C1E9 02       |SHR ECX,2      // ECX / 4 = 0x1E, counter
0065A3A6  |.  F3:AB         |REP STOS DWORD PTR ES:[EDI] // EDI points
to a HEAP of 0x32 bytes.
0065A3A8  |.  8BCA          |MOV ECX,EDX
0065A3AA  |.  83E1 03       |AND ECX,3
0065A3AD  |.  F3:AA         |REP STOS BYTE PTR ES:[EDI] // copies
another DWORD

- -----/


As we can see, in this part it takes the marker byte (0x7A), increments
it by 1 (0x7B) and copies the following byte (0x41) the number of times
indicated by the marker byte, but the buffer has only 0x32 bytes
allocated. Below those 0x32 bytes we find the header of another chunk on
the heap:

/-----
01355570  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  // beginning
of the 0x32 bytes heap
01355580  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
01355590  AB AB AB AB AB AB AB AB 00 00 00 00 00 00 00 00
013555A0  20 00 07 00 01 04 EE FE 78 02 C6 00 78 02 C6 00
013555B0  EE FE EE FE EE FE EE FE EE FE EE FE EE FE EE FE
013555C0  EE FE EE FE EE FE EE FE EE FE EE FE EE FE EE FE

- -----/


0x31355A0 is the beginning of the header of the next chunk. After
executing REP STOS, the corruption of the header of that chunk occurs:

/-----
013555D8  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41
013555E8  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41
013555F8  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41
01355608  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41
01355618  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41
01355628  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41
01355638  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41
01355648  41 41 41 41 41 41 41 41 EE FE EE FE EE FE EE FE

- -----/


The error is the following: since it copies DWORDs, instead of copying
0x1E bytes, it should have copied 0x0F bytes (0x1E / 2). Finally, the
heap block is allocated in this part of the code:

/-----
005AC5F7    56              PUSH ESI          // Heap Size
005AC5F8    6A 08           PUSH 8            // HEAP_ZERO_MEMORY
005AC5FA    FF35 A4347900   PUSH DWORD PTR DS:[7934A4]  // Heap
005AC600    FF15 84726E00   CALL DWORD PTR DS:[<&KERNEL32.HeapAlloc>]  ;
ntdll.RtlAllocateHeap

- -----/



9. *Report Timeline*

. 2010-05-27:
Core Security Technologies notifies XnView of the vulnerability.

. 2010-05-27:
The XnView author acknowledges receipt of the notification.

. 2010-05-27:
Core sends a technical description of the vulnerability, and a
Proof-of-Concept file that triggers the bug.

. 2010-05-28:
The XnView author notifies Core that the vulnerability has been fixed,
and that a fixed version will be released.

. 2010-06-02:
Core asks XnView when the fixed version will be released, in order to
coordinate the publication of the advisory with the release of a fixed
version.

. 2010-06-03:
The XnView author responds that version 1.97.5 will be available in 2
weeks.

. 2010-06-03:
Core requests a more precise date for the release, and reschedules
publication of its advisory to June 14th, 2010.

. 2010-06-07:
The XnView author responds that the update will be available on June 14th.

. 2010-06-10:
Core sends a second Proof-of-Concept, and asks the XnView author if it
triggers a different vulnerability.

. 2010-06-11:
The XnView author responds that the second PoC triggers the same
vulnerability.

. 2010-06-14:
Advisory CORE-2010-0514 is published.



10. *References*

[1] XnView website
[http://www.xnview.com/]
[2] Proof of Concept files
[http://www.coresecurity.com/files/attachments/CORE-2010-0514-Xnview-PoCs.rar]
[3] MBM file format
[http://software.frodo.looijaard.name/psiconv/formats/MBM_File.html]
[4] Basic elements: LListL
[http://software.frodo.looijaard.name/psiconv/formats/Basic_Elements.html#LListL]
[5] Paint Data Section
[http://software.frodo.looijaard.name/psiconv/formats/Paint_Data_Section.html#Paint%20Data%20Section]


11. *About CoreLabs*

CoreLabs, the research center of Core Security Technologies, is charged
with anticipating the future needs and requirements for information
security technologies. We conduct our research in several important
areas of computer security including system vulnerabilities, cyber
attack planning and simulation, source code auditing, and cryptography.
Our results include problem formalization, identification of
vulnerabilities, novel solutions and prototypes for new technologies.
CoreLabs regularly publishes security advisories, technical papers,
project information and shared software tools for public use at:
[http://corelabs.coresecurity.com/].


12. *About Core Security Technologies*

Core Security Technologies develops strategic solutions that help
security-conscious organizations worldwide develop and maintain a
proactive process for securing their networks. The company's flagship
product, CORE IMPACT, is the most comprehensive product for performing
enterprise security assurance testing. CORE IMPACT evaluates network,
endpoint and end-user vulnerabilities and identifies what resources are
exposed. It enables organizations to determine if current security
investments are detecting and preventing attacks. Core Security
Technologies augments its leading technology solution with world-class
security consulting services, including penetration testing and software
security auditing. Based in Boston, MA and Buenos Aires, Argentina, Core
Security Technologies can be reached at 617-399-6980 or on the Web at
[http://www.coresecurity.com].


13. *Disclaimer*

The contents of this advisory are copyright (c) 2010 Core Security
Technologies and (c) 2010 CoreLabs, and may be distributed freely
provided that no fee is charged for this distribution and proper credit
is given.


14. *PGP/GPG Keys*

This advisory has been signed with the GPG key of Core Security
Technologies advisories team, which is available for download at
[http://www.coresecurity.com/files/attachments/core_security_advisories.asc].

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.14 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iEYEARECAAYFAkwWj7IACgkQyNibggitWa1e5ACgo5+9x+0d52kMcG/W+SUMQBi2
654AoJ5SFLW+h9mSS84bHqpzqhxBwhB0
=HDp/
-----END PGP SIGNATURE-----

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